For many years there has been experimental evidence that anticancer alkylating agents cause cross-linking of DNA to protein, nd additional evidence has been obtained during recent years. Although the extent of this cross-linking is extensive in some instances, little is known about the molecular sites on the DNA and the proteins that are cross-linked, and the role of such cross-linking in determining cytotoxicity is not established. Although there is evidence that removal or repair of such cross-links occurs, essentially nothing about the molecular mechanism of such repair is known. Neither is it known whether inhibition of such repair would increase cytotoxicity and improve therapeutic utility of the agents. There is evidence that the extents of DNA-protein cross-linking and repair of such cross-linking differ for various agents. We propose to undertake the identification of the sites on the DNA and on the proteins that are cross-linked when cultures L1210 leukemia cells and ascites L1210 cells in mice are treated with nitrosoureas, nitrogen mustard, L-phenylalamine mustard, cyclophosphamide (in vivo) and platinum compounds. We will attempt to compare the extents of DNA-protein cross-linking in the linker and the nucleosomal coresof chromatin and in drug-sensitive and drug-resistant cells. We will study the removal or repair of the cross-links and seek means of inhibiting such repair with the aim of improving chemotherapy with these agents.